The present invention relates to semiconductor device fabrication and, more specifically, to device structures and design structures for a silicon controlled rectifier, as well as methods for fabricating a silicon controlled rectifier.
Chips with complementary metal-oxide-semiconductor (CMOS) devices may be exposed to electrostatic discharge (ESD) events, which can lead to potentially large and damaging ESD currents within the integrated circuit. Shrinking device dimensions have increased the susceptibility of integrated circuits to ESD events. Precautions may be taken by manufacturers, assemblers, and users of integrated circuits to avoid causing ESD events such as incorporating ESD prevention into the integrated circuit. The ESD protection device may prevent damage to the chip during post-manufacture handling until installation on a circuit board and even while the chip is installed on the circuit board. In the absence of an ESD event, the ESD protection device maintains a high-impedance, non-conductive state and is electrically isolated from the protected integrated circuit. If an ESD event is detected, the ESD protection device is configured to change to a low-impedance, conductive state to direct the ESD current to ground and away from the sensitive internal circuits of the chip. The ESD protection device is configured to maintain the conductive state until the ESD current is drained and the ESD voltage is discharged to an acceptable level.
One common type of ESD protection device is a silicon controlled rectifier (SCR), which offers both low capacitance and high failure currents. A silicon controlled rectifier may be constructed in CMOS technologies to provide ESD protection in integrated circuits that include inverters or other logic gates. A silicon controlled rectifier is characterized by a trigger voltage/current and a holding voltage/current, which determine the device responsiveness and effectiveness during an ESD event.
Improved device structures, fabrication methods, and design structures are needed for a silicon controlled rectifier.